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.Dd March 11, 2019
.Dt HUMANIZE_NUMBER 3
.Os
.Sh NAME
.Nm dehumanize_number ,
.Nm humanize_number
.Nd format a number into a human readable form and vice versa
.Sh SYNOPSIS
.In stdlib.h
.Ft int
.Fn dehumanize_number "const char *str" "int64_t *result"
.Ft int
.Fn humanize_number "char *buffer" "size_t len" "int64_t number" "const char *suffix" "int scale" "int flags"
.Sh DESCRIPTION
The
.Fn humanize_number
function formats the signed 64 bit quantity given in
.Fa number
into
.Fa buffer .
A space and then the
.Fa suffix
.Pq "if not null"
is appended to the end.
.Fa len
gives the size of the
.Fa buffer .
.Pp
If the formatted number (including
.Fa suffix )
would be too long to fit into
.Fa buffer ,
then repeatedly divide
.Fa number
by 1024 until it will fit.
In this case, prefix
.Fa suffix
with the appropriate SI designator.
.Pp
The prefixes are:
.Bl -column "Prefix" "Description" "Multiplier" -offset indent
.It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier"
.It k	kilo	1024
.It M	mega	1048576
.It G	giga	1073741824
.It T	tera	1099511627776
.It P	peta	1125899906842624
.It E	exa	1152921504606846976
.El
.Pp
.Fa len
must be at least 4 plus the length of
.Fa suffix ,
in order to ensure a useful result is generated into
.Fa buffer .
To use a specific prefix, specify this as
.Fa scale
(Multiplier = 1024 ^ scale).
The
.Fa scale
must be at least 0 and no more than 6.
.Pp
Alternatively, one of the following special values may be given as
.Pa scale :
.Bl -tag -width Dv -offset indent
.It Dv HN_AUTOSCALE
Format the buffer using the lowest multiplier possible.
.It Dv HN_GETSCALE
Return the prefix index number (the number of times
.Fa number
must be divided to fit) instead of formatting it to the buffer.
That is, the
.Fa scale
that would have been used if
.Dv HN_AUTOSCALE
had been used.
.El
.Pp
The following flags may be passed in
.Pa flags :
.Bl -tag -width Dv -offset indent
.It Dv HN_DECIMAL
If the final numeric result is less than 10,
and is not the same as the original value (that is, it has been scaled)
display it using a decimal radix character, and one following digit.
.It Dv HN_NOSPACE
Do not put a space between
.Fa number
and the prefix.
.It Dv HN_B
Use 'B' (bytes) as prefix if the original result does not have a prefix.
.It Dv HN_DIVISOR_1000
Divide
.Fa number
with 1000 instead of 1024.
That is, use decimal scaling instead of binary.
.El
.Pp
To generate the shortest meaningful value,
a buffer length
.Pq Fa len
that is 6 greater the length of the
.Fa suffix
along with
.Dv HN_AUTOSCALE
will ensure the highest meaningful scale is used.
Allow one extra byte for the sign if the number is negative,
and one less if the
.Dv HN_NOSPACE
flag is used.
.Pp
The
.Fn dehumanize_number
function parses the string representing an integral value given in
.Fa str
and stores the numerical value in the integer pointed to by
.Fa result .
The provided string may hold one of the suffixes, which will be interpreted
and used to scale up its accompanying numerical value.
.Sh RETURN VALUES
.Fn humanize_number
returns the number of characters stored in
.Fa buffer
(excluding the terminating NUL) upon success, or \-1 upon failure.
If
.Dv HN_GETSCALE
is specified, the prefix index number will be returned instead.
.Pp
.Fn dehumanize_number
returns 0 if the string was parsed correctly.
A \-1 is returned to indicate failure and an error code is stored in
.Va errno .
.Sh ERRORS
.Fn dehumanize_number
will fail and no number will be stored in
.Fa result
if:
.Bl -tag -width Er
.It Bq Er EINVAL
The string in
.Fa str
was empty or carried an unknown suffix.
.It Bq Er ERANGE
The string in
.Fa str
represented a number that does not fit in
.Fa result .
.El
.Sh SEE ALSO
.Xr strsuftoll 3 ,
.Xr orders 7 ,
.Xr humanize_number 9
.Sh HISTORY
.Fn humanize_number
first appeared in
.Nx 2.0 .
.Pp
.Fn dehumanize_number
first appeared in
.Nx 5.0 .